I am hoping some of the British experts out there can help me. I am trying to find out if the British used time delay fuzes on their trench mortar shells, mines and artillery shells. I would include Stokes mortar shells in this request. I am looking at the time period of September-October 1915. I have come across several references to the use of time delay fuzes during bombardments of the German trenches.

I would appreciate anyone who might have some knowledge on this subject to let me know when these might have been in use and any details on their operation. Thanks for taking the time to look this request over.

Drop me an email on my normal personal address and let me know exactly what you want. I'm up at the school shortly and will dig into my archive there for you. I may have some pictures of ones I've dealt with over the years that you can have if you like.

Any chance of your popping over to Plug St this year? We've had one dig there already in March I'll send you some pic's.

Just expanding on the above, a 'time delay fuze' is an oxymoron. Time fuzes were used to burst shells in the air, that said British time fuzes did have a Graze setting as an alternative function. It's a fairly common error to assume that a delay fuze has some sort of timer that starts running after impact. It's not that sophisticated, basically in delay mode the ignition/detonation 'chain' is mechanically interrupted to delay it.

Graze fuze work differently the ignition/detonation 'chain' is designed to be slow but doesnt need heavy 'impact', going through any solid material slows the shell and this activates the fuze to initiate shell detonation after a very short time, in other words tha action is designed to be slower than a normal impact shell and dosn't need a solid hit on the nose.

Not sure what you mean by mines but suspect it is in the German sense of a type a projectile not 'mine' as it is used in English.

What about fuzes for AP rounds designed to pierce armour and explode inside?

I've seen drawings of modern APHEI rounds with a deceleration-driven firing pin striking a primer, initiating a delay element of a millisecond or three, before this fires the main detonator through a septum into a nitrocellulose gaine.

Interests:The Great War - Mostly the land war - Mostly the German side - Mostly the Western Front Especially: Flame throwers, Special formations; Pioniere Sturm=Truppen Jaeger, usw.

Posted 27 April 2012 - 12:17 PM

The only time delay shells I know anything about in WW I were the fort-busting shells for the German 42 cm howitzers, which had several models of shell. From memory these could have weighted as much as 2550 lbs (the two main models of gun, the Gamma and the M Type, had different weights of shell); the Gamma gun, emplaced, weighted about 175 tons and could handle quite a weight of shell. These shells ware armored and could punch as much as 40 feet through a mix of armor plate, concrete, earth, interior walls, and corridors and internal spaces, after decending almost vertically from about 5 miles up; and had two compartments of explosives, each with its own time fuse, to maximize the probability of detonation. I only know of one example where both fuzes failed to explode. I have read a description where Belgian soldiers observed one of these monsters sliding down an underground corridor towards them, emitting smoke, but both fuzes failed; I am sure the Belgians soiled their pants.

My grand-father was the ID in the Generalkommando of the III. Reservekorps at the siege of Antwerp, and as such was responsible for supplying these shells to the big siege guns. As he had a staff car and a deputy to "watch the shop", he frequently went out to these batteries while they were firing on the Belgian forts. As a former heavy artillery NCO and Oberfeuerwerker in the foot artillery of the Prussian Army and Prussian Guard, he found these big guns, and the German and Austrian 30.5 cm mortars, fascinating. I have letters he wrote at quarters at night after conducting these visits.

The "Bomb: H.E.R.L 180 lbs Mk 1 - Heavy Case Armour Piercing" came with 2 alternative fuses one of which was "No5 Mk. I 2.5 second delay" (Air Ministry leaflet no 85 July 1918). It, it is stated, was to be used for "Special Operations" and I believe that this included attacks on ships with armoured decks and the weapon was sometimes referred to as a Battleship Bomb.

I am hoping some of the British experts out there can help me. I am trying to find out if the British used time delay fuzes on their trench mortar shells, mines and artillery shells. I would include Stokes mortar shells in this request. I am looking at the time period of September-October 1915. I have come across several references to the use of time delay fuzes during bombardments of the German trenches.

I would appreciate anyone who might have some knowledge on this subject to let me know when these might have been in use and any details on their operation. Thanks for taking the time to look this request over.

Ralph

Is this in the sense of a booby trap, Ralph? Intended to explode well after the projectile lands?

Thanks for all of the great replies. In the instances I am studying the author appears to indicate that the fuzes were designed to explode a short time after impact. One item was what the Germans called a mine, more than likely something along the lines of a Stokes mortar shell as it was small enough to pick up and toss outside the trench before detonating. I am aware of the use of time fuzes on shrapnel shells but I was not aware of any use in artillery shells in general as they were designed to explode on impact, or so I thought.

There was more than one reference to the delay in the fuze detonating and the reference to a large number of mortar rounds being fired as well as shells up to 38cm.

I do not know if trench mortar shells would have the need for a time fuze in the manner of a shrapnel shell or if it could have been something as simple as the shell hitting soft mud and failing to explode until tossed out to harder ground. If I come across any other references that could help I will pass them along.

Presumably you are talking about anything other than a percussion fuze?

The majority were Time and Percussion so would explode when they hit the ground regardless of the time set (if it hit the ground before the time set), except in misfires I would guess.

I think you'll find 'Percussion' was a portmanteau word that could mean Direct Action or Graze. AFAIK there were no UK DA fuzes with a Delay option until the L32 c.1965, in WW2 delay was achieved by firing No 117 or 119 with 'cap on'.

Of course 'most' fuzes were not T&P, HE was the most widely used ammo and percussion was the normal fuze. Time fuzes were introduced in limited number for HE to enable airburst ranging, but igniferous fuzes were nowhere near consistent enough to provide the low airburst needed for anti-personnel effects although there had been some optimistic early hopes that proved unfounded by reality. Of course Graze fuzes had the advantage that they could be used to get HE airburst by richochet fire, DA fuzes set to Delay are nowhere near as useful for this due to the need for DA from a steeper angle of descent.

The No 100 series of percussion fuzes were Graze whereas No 106 was DA. Shrapnel used Graze so that the shells penetrated a wall or gun shield before functioning - not much point in DA! Eventually it became normal UK practice not to include a percussion option for time fuzes used in cargo munitions such as star/illuminating - one mustn't wasted the British taxpayers' money.

Thanks for all of the great replies. In the instances I am studying the author appears to indicate that the fuzes were designed to explode a short time after impact. One item was what the Germans called a mine, more than likely something along the lines of a Stokes mortar shell as it was small enough to pick up and toss outside the trench before detonating. I am aware of the use of time fuzes on shrapnel shells but I was not aware of any use in artillery shells in general as they were designed to explode on impact, or so I thought.

There was more than one reference to the delay in the fuze detonating and the reference to a large number of mortar rounds being fired as well as shells up to 38cm.

I do not know if trench mortar shells would have the need for a time fuze in the manner of a shrapnel shell or if it could have been something as simple as the shell hitting soft mud and failing to explode until tossed out to harder ground. If I come across any other references that could help I will pass them along.

Ralph

Many of the early mortars fired by all sides used a time rather than an impact fuse. The most primitive of these was the old fashioned "fizzing wick" style either ignited by the gunner's cigarette before firing or by the flash of the propellant when firing. There are instances down the ages of soldiers getting to these after they have landed and either nipping off the fuse or heaving the projectile over the parapet (or overboard). Indeed some early VCs were won in this fashion in the Crimean war and even earlier the British sailor Lord Cochrane (upon whose exploits many fictional sailors such as Hornblower and Jack Aubery are based) is reputed to have dealt with a mortar shell in this fashion. Similar cases occurred in WW1. The introduction of internal time fuses initiated by mechanical means made such methods of dealing with mortar shells less feasible but shells were still sometimes thrown out of trenches before exploding. It has been said that some of the early British toffee apple (2 inch mortar) shells failed because they landed on soft ground - however this is incorrect as these had time and not impact fuses, the problem was that when firing over a short range with reduced propellant the shock of firing was insufficient to initiate the fuse. Safe (for the gunner) impact fuses were developed for most if not all trench mortars (including for the toffee apple) but time fuses were not abandoned as there were still instances where these were more useful. For instance when using the mortars for wire clearing it was considered more effective if the projectile was well bedded into the wire entanglement before exploding , in such a case its very position would preclude any enemy soldier doing anything about it before it exploded.

Interests:First World War in general, Somme specifically. War memorials and losses.

Posted 28 April 2012 - 10:42 AM

I think you'll find 'Percussion' was a portmanteau word that could mean Direct Action or Graze. AFAIK there were no UK DA fuzes with a Delay option until the L32 c.1965, in WW2 delay was achieved by firing No 117 or 119 with 'cap on'.

Of course 'most' fuzes were not T&P, HE was the most widely used ammo and percussion was the normal fuze. Time fuzes were introduced in limited number for HE to enable airburst ranging, but igniferous fuzes were nowhere near consistent enough to provide the low airburst needed for anti-personnel effects although there had been some optimistic early hopes that proved unfounded by reality. Of course Graze fuzes had the advantage that they could be used to get HE airburst by richochet fire, DA fuzes set to Delay are nowhere near as useful for this due to the need for DA from a steeper angle of descent.

The No 100 series of percussion fuzes were Graze whereas No 106 was DA. Shrapnel used Graze so that the shells penetrated a wall or gun shield before functioning - not much point in DA! Eventually it became normal UK practice not to include a percussion option for time fuzes used in cargo munitions such as star/illuminating - one mustn't wasted the British taxpayers' money.

Is there a distinction made between the graze and the direct action which really have the end the same effect, sudden stopping or slowing down by hitting the ground or by striking an object. There is no appreciable time delay. The only work I have to go on is the Treatise of Ammunition 1915 and a few articles culled from other publications and I can't find graze refferred to.

Yes there is a very definite difference between Graze and DA. Before 1914 shrapnel was the primary munition and Graze was the impact solution, as the amount of HE increased from Sep 1914 onwards the need for impact fuzes increased. The No 100 series of Graze fuzes was introduced in 1915 (th No 80/44 was a bit of a disaster), probably because Graze technology was well established. Graze is what caused the cratering and few fragments above ground, that's why DA was introduced with the No 106 fuze in 1916. The 1915 HB reflects pre 106 era.

What fuse might have been used if one wanted a howitzer shell to penetrate into a few yards of chalk before exploding? I assume a 101/102 graze fuse? Are there any studies as to their effectiveness, e.g. pre-July 1916? I ask because of the section about 'delayed action' fuses and their possible use on pages 60-61 of Peter Barton's 'The Somme - a new panoramic perspective' (1st edition).

From the replies to this subject it would appear that the delay in detonation may have simply been soft ground or mud that prevented the fuze from being set off more than a particular type of fuze designed to detonate shortly after impaxt. Thanks for all of the replies.

I'm not sure what you mean? Graze is designed to overcome the problem of the projectile striking at an angle outside the operating limits of a normal DA fuze. A grazing impact will often involve the projectile glancing off the target or ground and as such when the fuze functions the shell is above ground or outside of a hard target. This would lead to a lessening in the size of any crater and an increase in the fragmentation due to the lack of tamping by the ground. To obtain better cratering, (at the cost of a much reduced fragmentation) a DA delay, (later to morph into the Super Quick / delay type fuze) would be required. I'll have someone look in our museum and see what ones they can find. We have both whole and cutaways of most fuzes that have been in service So I'll try and get some pictures.

The T of A 1915 does however make particular reference to the sensitivity of Graze Fuzes and precautions required to prevent premature functioning. looking at the technical specifications there appear to be a minimum of 2 safety arrangements (not including the safety pin) so these were starting to get towards the modern standards that we still abide by. The 106 as you state was post TA 1915 but the MkII had both a centrafugal collar and shearwire in addition to the safety cap. By the MkIV of course, the addition of shutter to interrupt the detonation chain had been added and therefore the fuze was up to the modern (minimum) standard.

If you wanted to create craters then graze was the only option, and this was the problem in the first half of WW1. Chalk is very soft, at the fuze testing facility on Salisbury Plain chalk shells were fired vertically and dropped base first (with impressive noise), these were inert shells (the fuzes were recovered for inspection) and they went 10+ feet into the ground.

Thanks for that. Peter Barton's argument is that, in order to destroy the German dugouts on the Somme prior to 1st July 1916, what was required was heavy howitzer shells to explode underground with the explosion, shock and gases killing or disabling the dugouts' occupants. This, he suggests, required the use of a 'delayed action' fuse. Did such a thing exist or are we talking about the natural delay between the activation of the graze fuse and the explosion of the shell and, if so, was this controllable at that time?

I'm being particularly thick today, (although so then are all the others here in work!). Are you saying that the only way to get the shell to function was to use a Graze type fuze because of it's sensitivity? If so why did we manufacture so many DA Fuzes? The T of A 1915 even goes as far as to say, "Usually these fuzes are required to act very quickly, before the shell has time to rise after glancing off the ground." If a DA fuze functions (and does not become a blind), then it is buried to some degree and therefore will create a larger crater than an identical shell that has functioned quicker and at less or no depth. As this is basic explosive engineering I fail to see how the normal facts have been reversed in your arguement?

Although graze fuzes may give a lower incidence of blinds, (I would have to look up the stats to confirm that though), to obtain a desent crater the shell needs to be buried to a reasonable depth which is where DA comes in. It is possible to bury a shell too far so that little or no effect is seen above ground but that is very difficult to achieve and rare in the exteme as a DA fuze will normally function on it's first contact with a solid object. Liquid mud will defeat a DA action but with a graze the fuze will often still function, however the give away is in the name and the liquid mud is rapidly replaced with more liquid mud. a shell buried to deep however does give excellent ground shock and is very good at destroying nearby trenches and works.

Maybe all the thousands of items I've blown up both on the surface or buried and tamped performed the wrong way!

Do you have a reference for the SPTA trial? I would love to see why they wanted to drop shell base first to see the depth penetration. Their trial programme seems very odd, and as such interesting in my studies. I would love to see the objectives and what conclusions they drew.

I must beginning to suffer in old age. As I understood it a Direct Action fuze was designed to produce a surface burst. A inertia fuzed shell had a built in delay of a few microseconds as the 'hammer' ran forward onto the striker as the shell was slowed,overcoming the anti-creep spring, and initiating the explosive chain. This allowed the shell to penetrate earthworks but caused cratering. A direct action fuze operated where the striker was driven directly onto a percussion cap and commenced the explosive chain. This gave a burst (oval in shape) producing a surface blast and shrapnel effect. I am ignoring delay caused by the operation of safety devices. Obviously any type of percussion fuze had a problem on very soft going Am I now being told this is wrong? SW

No you pretty much have it, but the Graze fuze as stated previously acted very quickly, "Usually these fuzes are required to act very quickly, before the shell has time to rise after glancing off the ground." There is always a slight delay whilst a DA fuze functions. It is not an intentional thing but caused by the technology of the day the action of the striker travelling back to impinge on the stab detonator and speed of the explosive train. This is but fractions of a second but should allow a DA fuzed shell to bury it's self or partially bury it's self, far enough so you get some cratering but not huge and the depth is not sufficient to 'tamp' the shell sufficiently to prevent a reasonable fragmentation. For proper cratering you need a DA Delay fuze. The 240mm Mortar was fitted with the Peuch - Remondy 24 31 Mod 1916 which had a 1/10th of a second delay. This was to achieve just this and allow better cratering and ground shock to enable better destruction of fortifications (fieldworks).

I had not considered the complete implications of fuzing in my studies, and this thread has now started a whole new line of research! I have contacted a colleague and asked him to look into the British use of DA Delay fuzes, when, where and on what natures of ammunition. Hopefully this will throw more light onto the subject, (and give me a steer as to my research).

I note the germans were using delayed action fuzes in 1916 with shells like the 7.7 Cm HE being fitted with the KZ and LKZ 16 mV with the mV being mit verzögerung (with delay). The technology race versus the raw materials available poses another interesting question.

I must beginning to suffer in old age. As I understood it a Direct Action fuze was designed to produce a surface burst. A inertia fuzed shell had a built in delay of a few microseconds as the 'hammer' ran forward onto the striker as the shell was slowed,overcoming the anti-creep spring, and initiating the explosive chain. This allowed the shell to penetrate earthworks but caused cratering. A direct action fuze operated where the striker was driven directly onto a percussion cap and commenced the explosive chain. This gave a burst (oval in shape) producing a surface blast and shrapnel effect. I am ignoring delay caused by the operation of safety devices. Obviously any type of percussion fuze had a problem on very soft going Am I now being told this is wrong? SW

Yep, that's basically right.

Pre-1914 there was no HE for 18 and 13 pr, not a lot for 4.5-in and 60-pr, and not many guns bigger than that. Shrapnel and star (and there wasn't much of the latter) needed a time fuze to burst in the air.

T&P (P being graze) P was an option to burst shrapnel behind light protection such as walls and gun shields and was considered OK for HE because it was the explosion to blow things up rather than the fragments that mattered.

One HE became prevalent (and predominant given that 18 pr was about 50/50), and fragmentation more important, then the graze as standard percussion fuzes were soon recognised as 'not the solution' because they caused too much cratering. Hence the No 106 Direct Action fuze that was the functional model for the standard fuze for decades to come. It did cause shallow craters, but nothing like graze did.

Obviously for heavy artillery, which was in the business of blowing stuff up, they were more happy with graze, although against targets in the forward area the infantry who had to plough through the craters probably had a view as well.

Interestingly RN and I think coast RGA seem to have used base instead of nose fuzes on their AP shells with an explosive fill, although these would have had a graze type action. Don't know (haven't looked) if base fuzes were used with superheavy arty on the W Front. If you wanted deep penetration then they'd probably be better than nose fuzes which were more vulnerable to impact damage causing malfunctions.

Of course using arty to destroy point targets wasn't a very good solution, but there wasn't an alternative in WW1. Probability theory is the god of all true gunners (I abase myself daily), and demands a lot of shells to hit a small target (not forgetting continuous observation to ensure the mpi doesn't drift away from the target as the gun warms, meteor changes, etc).

Obviously we are diametrically opposed in thought on this. I am taking the detail from the period documents I.E. the T of A 1915 which states that the graze action is very very quick. Now working from a standpoint of science that should mean that the Graze Action fuze should function at a lesser depth than the slower DA fuze therefore less crater. Now I may be wrong, (I think I was once before,(ATO EGO comming through))so if this is not the case please educate. Any references on the subject would be gratefully recieved as I think this need more work from me for my studies. I'm not quite sure what if any impact it might have but it needs looking into. PM me by all means and we can carry on the dull technical stuff separately if you wish.